threshold
Definitions
A strip of wood or stone forming the bottom of a doorway and crossed in entering a house or room.
The magnitude or intensity that must be exceeded for a certain reaction, phenomenon, result, or condition to occur or be manifested.
The beginning or initial stage of an event or process.
Examples
She stood on the threshold of a new career, feeling both nervous and excited.
The noise level in the room exceeded the threshold of what he could comfortably tolerate.